QPbe  WLtat  €nb  Association. 

REPORT  OF 
THE  COMMITTEE  ON  WATER  SUPPLY 


Avery  Architectural  and  Fine  Arts  Library 
Gift  of  Seymour  B.  Durst  Old  York  Library 


REPORT  OF 
THE  COMMITTEE  ON  WATER  SUPPLY 


ELIHU  CUNYNGHAM  CHURCH,  Ch 
CLIVE  WETHERILL  KERNAN 
OL1N  POTTER^GEER 
HAROLD  PERRINE 


3d  January,  1910. 


TP 


WLt&t  €nb  association. 


REPORT  OF 
THE  COMMITTEE  ON  WATER  SUPPLY. 


SOURCE  OF  SUPPLY. 

Collection.  All  the  water  which  we  use  originally  comes  from  the 
clouds  in  the  form  of  rain.  Part  of  the  rainfall  immediately  flows  over  the 
ground  into  the  streams,  and  is  known  as  "  surface  run-off " .  This  is  of 
course  greatest  when  the  ground  is  frozen.  The  remainder,  which  is  the 
principal  source  of  supply,  soaks  into  the  earth  as  into  a  sponge  and  is 
either  sucked  up  by  the  roots  of  trees  and  other  vegetation  and  re-evap- 
orated into  the  air,  or  else  it  continues  to  percolate  through  the  soil — later 
to  appear  in  the  form  of  springs.  These  feed  the  streams  even  during 
the  dry  seasons,  and  for  months  after  any  rain  has  fallen.  Thus  the 
ground  may  be  looked  upon  as  a  great  reservoir  storing  up  water  within 
itself,  later  to  be  given  out  gradually.  If  the  amount  of  rain  falling 
each  month  were  the  same  as  that  falling  during  each  of  the  other 
eleven  months  large  artificial  storage  reservoirs  would  not  be  required  and 
it  would  only  be  necessary  to  intercept  the  stream  flow  and  pipe  it  direct 
to  the  consumer.  This  is  not  the  case,  however.  A  stream  which  at 
one  season  of  the  year  is  so  small  that  it  may  be  crossed  on  step- 
ping stones  is  a  perfect  torrent  at  other  times.  But  not  only  does  the 
rainfall  vary  with  the  different  seasons,  it  also  varies  greatly  from  year  to 
year,  and  it  happens  that  the  rainfall  of  a  "dry  year"  may  be  only  60% 
of  that  which  falls  annually  under  average  conditions.  These  periods  of 
semi-drought  often  extend  over  two  or  three  consecutive  years  and 
require  careful  thought  on  the  part  of  the  Engineer  who  is  responsible  for 
the  water  supply  of  a  great  city,  that  he  may  have  sufficient  storage  to 
carry  him  safely  over  them.  On  the  other  hand  there  are  years  and 
series  of  years,  when  the  rainfall  is  excessive,  and  far  beyond  that  average 
which  can  ordinarily  be  relied  upon. 


In  order  to  impound  all  the  water  which  falls  in  any  catchment 
area  it  would  be  necessary  to  design  works  of  such  magnitude  that  there 
would  be  no  flow  over  the  waste  weir  at  the  end  of  the  period  of  great- 
est rainfall;  that  is  to  say,  that  the  reservoirs  would  be  just  full  at  the  end 
of  the  rainiest  hour  of  the  rainiest  day  of  the  rainiest  week  of  the  rainiest 
year.  Therefore  it  follows  that  at  all  other  times  the  reservoirs  will  be 
only  partially  full.  The  problem  is  whether  it  is  economically  advisable  to 
try  to  save  all  the  water,  or  whether  there  is  not  a  point  beyond  which 
additional  saving  is  unduly  expensive,  and  therefore  is  it  not  best  to 
design  the  impounding  reservoirs  with  an  eye  to  average  rather  than 
abnormal  conditions. 

The  whole  matter  resolves  itself  into  a  question  of  dollars.  The 
engineer  must  be  careful  not  to  develop  a  given  watershed  to  such  a 
degree  that  additional  savings  of  water  will  cost  more  per  gallon  than  the 
charge  for  a  like  quantity  when  obtained  from  some  other  source. 

The  layman  on  seeing  water  run  over  the  spillway  of  a  dam  is 
inclined  to  say :  "  If  they  had  only  built  it  a  few  feet  higher  they  could 
have  saved  all  that n ,  and  he  little  thinks  that  the  expense  of  the  extra 
height  is  not  to  be  measured  by  the  cost  of  the  top  courses  of  masonry 
(where  the  dam  is  only  a  few  feet  wide)  but  by  the  cost  of  the  bottom 
courses  of  masonry  where  the  dam  may  be  several  hundred  feet  wide  ; 
for  dams  like  high  buildings  are  designed  from  the  top  downward  that 
they  may  properly  withstand  the  weights  and  strains  imposed  upon  them. 

The  expense  of  such  structures  increases  in  a  way  so  out  of  all 
proportion  to  their  height  that  instead  of  placing  one  huge  dam  near  the 
mouth  of  a  stream  it  is  always  better  to  locate  separate  and  smaller  dams 
on  each  of  its  tributaries,  thus  creating  a  number  of  small  reservoirs  for 
temporary  storage.  This  has  been  done  in  the  Croton  watershed  and  that 
system  now  contains  no  less  than  ten  subsidiary  dams.  The  lakes 
thus  created  act  as  feeders,  impounding  the  water  until  such  time  as  it 
may  flow  into  the  main  storage  reservoir  to  best  advantage.  The 
Paterson  dam  will  serve  such  a  purpose,  but  with  its  completion  the 
development  of  the  Croton  watershed  will  have  reached  a  point  beyond 
which  it  will  probably  not  be  profitable  to  carry  it.  In  the  opinion  of 
your  Committee  the  construction  of  this  dam  is  most  advisable  as  it  will 
fully  develop  that  watershed. 


4 


DISTRIBUTION. 


Use.  Of  the  amount  of  water  brought  to  New  York  much  is  used, 
some  is  wasted,  and  a  little  is  lost.  The  demands  upon  the  system  for 
water  are  subject  to  great  fluctuation  ;  thus  the  amount  used  in  certain 
months  greatly  exceeds  the  average.  The  amount  of  water  which  may 
be  used  in  a  day  of  maximum  consumption  is  likely  to  reach  150%  of 
the  average  ;  and  it  is  no  unusual  thing  to  have  a  maximum  hourly 
demand  for  water  equal  to  1  75%  of  the  average.  That  merely  means  that 
more  water  is  used  in  certain  seasons  of  the  year  than  in  others ;  that  more 
water  is  used  on  certain  days  of  the  week,  Monday  for  instance,  than  at  other 
times  ;  and  that  the  requirements  of  the  different  hours  of  the  day  vary 
greatly.  Thus  the  flow  is  at  a  minimum  between  midnight  and  4  A.  M. 
It  increases  as  the  activities  of  the  day  begin  and  reaches  a  maximum 
in  the  forenoon  when  the  rate  of  consumption  is  greatest.  Water  is 
furnished  for  domestic,  commercial  and  public  purposes,  but  the  number 
of  gallons  used  each  day  per  capita  in  New  York  is  less  than  that  used 
in  most  of  our  prominent  cities.  New  York  is  called  upon  to  furnish 
great  quantities  of  water  to  a  large  floating  population ;  the  business  por- 
tion of  the  city  being  occupied  principally  by  people  whose  names  do 
not  appear  upon  the  New  York  census  returns  as  they  commute  from 
New  Jersey,  Staten  Island  and  Long  Island.  The  rapid  and  regular 
increase  in  the  population  of  the  city,  as  shown  by  successive  census 
returns  is  a  matter  which  has  been  taken  into  account  in  estimating  the 
quantity  of  water  which  will  be  needed  at  stated  intervals  in  the  future. 
The  most  careful  estimates  now  made  indicate  that  the  future  population 
of  this  city  will  be  as  follows : 

1910  -         -         -  4,625,000 

1915  -         -         -         -  5,250,000 

1020  -         -         -  5,875,000 

1925  -         -         -         -  6,500,000 

1930  -         -         -  7,125,000 


5 


BALTIMORE 


NEW  YORK 


ST.  LOUIS 


CINCINNATI 


BOSTON 


AVERAGE  DAILY  CONSUMPTION  OF  WATER 
PER  PERSON 


PRINCIPAL  CITIES  OF  THE  UNITEO  STATES 
1910 


CLEVELAND 


CHICAGO 


PHILADELPHIA 


Baltimore 

New  York 

St.  Louis 

Cincinnati 

Boston 

Cleveland 

Chicago 

Philadelphia 

Buffalo 


1904 
1904 
1902 
1904 
1904 
1903 
1902 
1904 
1902 


BUFFALO 

GALLONS 


Waste.  Much  of  the  so-called  waste  is  more  correctly  extrava- 
gant use.  Thus  water  is  allowed  to  run  freely  during  the  winter  to 
prevent  the  pipes  from  freezing  and  many  people  prefer  to  allow  the 
water  to  run  away  rather  than  go  to  the  expense  of  repairing  their 
plumbing  fixtures. 

Loss.  Some  water  is  undoubtedly  lost  through  leaky  pipes  and 
reservoirs.  Practically  all  of  the  pipes  which  were  exposed,  however, 
during  the  construction  of  the  subway  appeared  to  be  in  good  condition  and 
it  was  evident  that  the  loss  from  the  joints  of  the  pipe  system  was  very 
small  in  amount.  A  break  in  the  distributing  system  generally  makes  itself 
apparent  at  once,  either  by  appearing  through  the  street  surface,  or  by 
flooding  the  surrounding  cellars,  or  by  washing  away  the  soil  and  causing 
the  pavement  to  sag  into  the  resulting  cavity.  Many  opinions  have  been 
advanced  concerning  the  amount  of  water  daily  wasted  in  New  York 
and  the  estimates  have  varied  from  15%  to  50%  of  the  total 
consumption.  Those  who  estimate  the  waste  at  the  larger  figure 
have  maintained  that  if  this  loss  can  be  stopped  the  present  sources 
of  supply  would  be  adequate  for  many  years  to  come.  Some  claim  that 
the  night  flow  is  the  measure  of  waste,  as  very  little  water  is  being  used 
for  domestic  and  manufacturing  purposes  during  those  hours.  Many 
buildings  of  certain  classes  in  New  York  are  equipped  with  storage 
tanks  upon  the  roof,  varying  anywhere  from  ten  to  forty  thousand  gallons 
capacity,  which  are  called  upon  to  supply  the  buildings  with  water  during 
those  periods  of  the  day  when  the  pressure  is  low  in  the  service  mains, 
due  to  the  large  quantities  of  water  being  used.  These  tanks  are  filled 
during  the  hours  of  the  night  when  the  pressure  is  again  normal  and  that  in 
our  opinion  accounts  for  a  large  proportion  of  the  night  flow.  Much 
water  is  also  used  at  night  all  the  year  around  by  power  plants,  and 
during  the  winter  time  for  steam  heating  and  other  purposes. 

ADDITIONAL  SUPPLY. 

The  most  reliable  figures,  which  make  preventible  waste  under 
15%,  show  that  were  it  possible  to  stop  all  waste,  the  resultant  saving  in 
water  would  not  be  sufficient  to  enable  the  city  to  get  along  with  the 
supply  which  the  Croton  watershed  is  safely  able  to  furnish.    The  city 


8 


authorities  have  realized  this  and  have  made  investigations  concerning  the 
best  sources  of  additional  supply.  Interstate  water  is  not  available  and 
the  city  has  therefore  been  obliged  to  eliminate  Ten  Mile  River  and  the 
Delaware  River  from  consideration.  With  the  passage  of  the  Smith 
Bill  the  city  was  forbidden  to  develop  the  watersheds  east  of  the  Hudson 
river,  including  those  in  Dutchess  County.  The  Catskills  were  next  looked 
to  as  the  possible  source  of  supply  and  their  watersheds  are  now  being 
developed  to  meet  the  demands  which  the  city  is  already  making  for 
additional  water.  In  the  opinion  of  your  Committee  this  work  has  not 
been  undertaken  any  too  soon,  and  its  progress  is  highly  satisfactory. 

Some  not  familiar  with  the  situation  have  criticised  the  Board 
of  Water  Supply  under  the  impression  that  they  are  developing 
a  watershed  on  the  west  side  of  the  river  before  satisfying  them- 
selves that  it  is  possible  to  conduct  the  water  across  the  Hudson  to 
New  York.  There  has  never  been  any  question  as  to  the  possibility  of 
getting  the  water  across  the  Hudson.  The  only  problem  confronting  the 
engineers  is  which  of  the  four  possible  methods  will  be  the  most  satisfac- 
tory ;  for  it  is  possible  to  employ  ( 1 )  a  bridge  to  carry  the  pipes  (2)  or 
lay  pipes  on  the  bed  of  the  river  (3)  or  construct  either  a  shallow  tunnel 
(4)  or  a  deep  tunnel  through  solid  rock.  The  deep  tunnel  would  not  be 
hampered  in  its  construction  by  many  of  the  difficulties  connected  with 
sub-aqueous  work. 

The  cost  of  condemnation  proceedings  in  the  Catskills  has  been  very 
severely  criticised  but  not  being  an  engineering  matter  is  respectfully 
referred  to  the  Committee  on  Legislation,  Law  and  Schools,  as  the  remedy 
for  such  conditions  is  by  means  of  a  legislative  enactment.  The 
Board  of  Water  Supply  is  not  in  any  way  connected  with  the  work  of 
condemnation. 

ACQUEDUCT  UNDER  NEW  YORK. 

The  plan  for  conducting  the  water  from  the  Hill  View  reservoir 
at  the  northern  limit  of  the  city  and  distributing  it  to  the  service  pipes  has 
received  our  careful  consideration.  The  problem  to  be  solved  by  the 
engineers  of  the  Board  of  Water  Supply  is  one  of  moving  large  quan- 
tities of  water  in  bulk  (500,000,000  gallons  daily)  from  the  reservoir  to 


9 


the  various  distributing  points,  where  the  Department  of  Water  Supply,  an 
entirely  different  Bureau,  takes  charge  of  it  and  delivers  it  to  the  consumers 
through  the  street  pipes.  In  the  Report  of  the  Board  of  Water  Supply  of 
October  9,  1 905,  it  was  tentatively  proposed  to  conduct  part  of  the 
500,000,000  gallons,  namely  120,000,000  gallons,  daily  to  Brooklyn  by 
means  of  a  pipe  line.  The  Board  states  "  It  is  possible  that  studies 
made  more  in  detail  will  indicate  some  modification  of  this  line  to  be 
advisable,  and  the  precise  form,  dimensions  and  locations  best  adapted  for 
the  proposed  terminal  reservoirs  of  the  acqueduct  system  in  Brooklyn  and 
on  Staten  Island,  remain  as  subjects  for  further  study.  The  main  distrib- 
uting lines  from  Hill  View  reservoir  to  the  Boroughs  of  Manhattan, 
Queens  and  the  Bronx  are  matters  for  later  consideration".  It  is  thus 
seen  that  the  treatment  of  the  remaining  380,000,000  gallons  daily  had 
not  at  that  time  been  decided  upon.  Later  it  was  found  advisable  to 
abandon  the  tentative  plan  for  the  pipe  line  and  conduct  all  the  water 
into  the  city  through  a  large  tunnel  which  was  to  be  constructed  at  suit- 
able depth  in  the  rock  formation  under  the  city.  This  can  in  no  way  be 
called  a  "change  of  plan,"  because  at  the  time  of  the  Report  mentioned 
the  Board  had  not  reached  any  definite  decision  as  to  the  best  way  of 
conducting  this  water,  and  the  present  plan  is  the  result  of  complete  exam- 
inations and  investigations  made  since  that  date.  The  only  change  is  the 
abandonment  of  the  tentative  plan  to  carry  1 20,000,000  gallons  daily  by 
a  pipe  line  to  Brooklyn  and  Richmond.  This  change  is  advisable  for  a 
number  of  reasons. 

The  cost  of  the  deep  rock  tunnel  will  be  much  less  than  that  of  any 
system  of  piping.  The  openings  to  the  tunnel  will  be  upon  property 
owned  by  the  city.  The  work  of  tunneling  will  be  conducted  at  con- 
siderable depths  without  that  inconvenience  to  business  and  transportation 
which  results  whenever  the  streets  of  the  city  are  disturbed  for  the  purpose 
of  laying  pipes.  A  rock  tunnel  of  this  character  is  one  of  the  most  per- 
manent structures  that  engineers  can  build.  It  is  at  once  practical,  safe, 
economical  as  to  first  cost,  and  maintenance  charges  will  be  at  a  mini- 
mum. The  disadvantages  attending  the  alternative  plan  of  bringing 
water  from  the  reservoir  to  the  distributing  points  in  a  considerable 
number  of  large  iron  or  steel  pipes  (72"  pipes  would  be  required) 
are  very  great.    The  cost  of  the  work  would  be  excessive  as  the 


10 


streets  of  New  York  are  already  so  filled  with  pipes  and  subsurface 
structures  that  placing  these  mains  would  be  costly.  The  incidental 
damage  done  to  business  interests  in  those  streets  which  would  be  ripped 
up  for  the  purpose  would  be  exceedingly  great.  The  loss  to  merch- 
ants and  property  owners  on  42nd  Street  during  the  construction  of  the 
present  subway  tunnels  indicates  what  might  be  expected.  It  has  been 
proposed  to  "kill  two  birds  with  one  stone"  and  place  these  mains  in 
excavations  built  for  future  subways,  that  is,  construct  the  subway  at  the 
same  time  the  water  mains  are  installed.  We  all  know  the  damage  that 
results  when  a  water  main,  even  as  small  as  24"  in  diameter  is  broken. 
Should  a  leak  occur  in  one  of  these  72"  pipe  the  damage  which  would 
be  wrought  is  incalculable  and  it  is  practically  certain  that  all  persons 
riding  at  that  time  in  the  subway  would  be  drowned  like  rats  in  a  trap. 

ELIHU  CUNYNGHAM  CHURCH,  Chairman. 
CLIVE  WETHERILL  KERNAN, 
OLIN  POTTER  GEER, 
HAROLD  PERRINE, 


3d  January,  1910. 


1  1 


